Title 19 of the Mercer Island City Code is the City's Unified Land Development Code. This establishes allowed uses and development standards for each zoning district. This means that there is a list of allowed uses and development standards such as minimum lot size, dimensions, maximum gross floor areas, maximum impervious surface coverage and maximum height.

To See Zoning on a Specific Site: The location and boundaries of the various zones of the city are shown and delineated on the city of Mercer Island Zoning Map. To type in specific street addresses for zoning information, check out nwmaps.net.

The City of Mercer Island has four single-family zones, three multi-family zones, four commercial or mixed-use zones, and one public zone, consisting of the following:

Zone Type

Symbol

Minimum Lot Size

ULDC

Single Family

R-8.4

Minimum 8,400 SF lots.

19.02

Single Family

R-9.6

Minimum 9,600 SF lots.

19.02

Single Family

R-12

Minimum 12,000 SF lots.

19.02

Single Family

R-15

Minimum 15,000 SF lots.

19.02

Multi-Family, Limited

MF-2L

The maximum allowed density is 26 units per acre.

19.03

Multi-Family

MF-2

The maximum allowed density is 38 units per acre.

19.03

Multi-Family

MF-3

The maximum allowed density is 26 units per acre.

19.03

Business

B

No minimum lot size.

19.04.050

Planned Business

PBZ

No minimum lot size for non-residential uses; the average parcel size of residential lots shall be 7,200 SF.

19.04.010

Commercial Offices

C-O

No minimum lot size.

19.04.020

Public Institution

P

No minimum lot size.

19.05

Town Center

TC

No minimum lot size.

19.11

The single-family residential zoning districts allow specified uses and lot development. The minimum lot development standards for the single-family residential zoning districts are summarized in the following table:

Zoning Districts

Minimum Lot Size1

Minimum Lot Width

Minimum Lot Depth

R-8.4

8,400 SF

60 feet

80 feet

R-9.6

9,600 SF

75 feet

80 feet

R-12

12,000 SF

75 feet

80 feet

R-15

15,000 SF

90 feet

80 feet

(1 The shorelands part of any lot and any area of the lot that is part of a vehicular access easement shall be excluded in determining whether a lot complies with the lot's minimum area requirements.)

The following standards apply to all single family zoned property R-8.4, R-9.6, R-12, and R-15:

Minimum Front Yard Setbacks

Minimum Rear Yard Setbacks

Minimum Side Yard Setbacks

Minimum Setback From Public Rights-of-ways and vehicular access easements

Maximum Building Height2

Maximum Gross Floor Area3

20 feet

25 feet

The side yard setbacks must sum to 15 feet; provided that no side yard shall be less than 5 feet.

10 feet

30 feet

45% of net lot area.

(2 See Code for how height is calculated.)
(3 See Code for how Gross Floor Area is calculated.)

The total amount of impervious surface permitted on a residential lot is governed by the lot slope.

Lot Slope1

Lot Coverage
(limit for impervious surfaces)

Less than 15%

40%

15 – less than 30%

35%

30-50%

30%

Greater than 50% slope

20%

(1Lot Slope is calculated by subtracting the lowest elevation on a lot from the highest elevation, and dividing the resulting number by the shortest horizontal distance between these two elevation points.)

The above document(s) are Adobe® Acrobat® PDF files and may be viewed using the free Adobe® Acrobat® Reader™. Most newer web browsers already contain the Adobe® Acrobat® Reader™ plug-in. However, if you need it, click on the "Get Acrobat® Reader™" icon to download it now.